problem with Imaginary in sympy

[Xuemei Gu]

hey,

I wander whether one has occurred such problem: 

I define a initial state: 

state=a[1]*b[0]*c[0]*d[0]*1j+a[1]*b[0]*c[0]*d[0] + a[2]*b[1]*c[1]*d[1]     # for some reason I have to do such decomposition

datalist=state.as_coefficients_dict()   

I can get: 

            { FF2[0]*FF3[0]*FF4[0]: 1,  FF2[1]*FF3[1]*FF4[1]: 1,    I*FF2[0]*FF3[0]*FF4[0]: 1 } 

Now the problem is :

Because I is a Imaginary number, it's not a symbol. How can I get something such as  { FF2[0]*FF3[0]*FF4[0]: 1,  FF2[1]*FF3[1]*FF4[1]: 1,    FF2[0]*FF3[0]*FF4[0]: 1j} or { FF2[0]*FF3[0]*FF4[0]: 1+1j,  FF2[1]*FF3[1]*FF4[1]: 1 } 

Thank you very much!

 

[Aaron Meurer]

I was hoping something like collect(x*y + x, [x, y], evaluate=False)
would do what you want, but it doesn't quite.

You could create a Poly with the coefficients as variables and use
Poly.as_coefficients_dict.

Aaron Meurer

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[Xuemei Gu]

Thank you very much!

I have another question: 

I get a string list such as  setupstr='LI(OAMHolo(OAMHolo(XX,e,6),f,2),a,f)'

however in the string, LI OAMHolo are own defined functions, I don't know how to replace them as functions. 

I want to know how to do in sympy like I use ToExpression in Mathematica. 

Thank you very much!

best regards

Mei

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Xuemei Gu
PhD Student

State Key Laboratory for Novel Software Technology, Nanjing University

163 Xianlin Avenue, Qixia District, 210023, Nanjing City, China  

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[Oscar Benjamin]

You can do it like this:

In [7]: setupstr='LI(OAMHolo(OAMHolo(XX,e,6),f,2),a,f)'

In [8]: from sympy import S

In [9]: S(setupstr)
Out[9]: LI(OAMHolo(OAMHolo(XX, e, 6), f, 2), a, f)

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[Xuemei Gu]

Thank you very much, I tried this, but it doesn't work. It only give the output but the the functions (LI,  OAMHolo) are not executed.

For simple example

stringA='3+4'

S(stringA)

It will give you the results 7.  It's correct but in my case these functions don't work.

I made a question in stackoverflow about the question, which make more clear:

https://stackoverflow.com/questions/55520809/how-to-implement-a-function-with-pythonsympy-realizing-the-same-as-toexpressi 

Did I misunderstand?  Thank you very much! 

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[Aaron Meurer]

I answered on StackOverflow. You can pass in custom functions as the
second argument to sympify().

Aaron Meurer

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